Magnetic resonance imaging (MRI) involves the transmission and receipt of radio frequency (RF) energy. RF energy may be transmitted by a coil. Resulting magnetic resonance (MR) signals may also be received by a coil. In early MRI, RF energy may have been transmitted from a single coil and resulting MR signals received by a single coil. Later, multiple receivers may have been used in parallel acquisition techniques. Similarly, multiple transmitters may have been used in parallel transmission (pTx) techniques.
RF coils create the B1 field that rotates the net magnetization in a pulse sequence. RF coils may also detect precessing transverse magnetization. Thus, RF coils may be transmit (Tx) coils, receive (Rx) coils, or transmit and receive (Tx/Rx) coils. An imaging coil should be able to resonate at a selected Larmor frequency. Imaging coils include inductive elements and capacitive elements. The inductive elements and capacitive elements have been implemented according to existing approaches using two terminal passive components (e.g., capacitors). The resonant frequency, v, of an RF coil is determined by the inductance (L) and capacitance (C) of the inductor capacitor circuit according to equation (1):
                    v        =                  1                      2            ⁢            π            ⁢                          LC                                                          (        1        )            
Imaging coils may need to be tuned. Tuning an imaging coil may include varying the performance of a capacitor. Recall that frequency: f=ω/(2π), wavelength: λ=c/f, and λ=4.7 m at 1.5 T. Recall also that the Larmor frequency: f0=γB0/(2π), where γ/(2π)=42.58 MHz/T; at 1.5 T, f0=63.87 MHz; at 3 T, f0=127.73 MHz; at 7 T, f0=298.06 MHz. Basic circuit design principles include the fact that capacitors add in parallel (impedance 1/(jCω)) and inductors add in series (impedance jLω).
In existing systems, when MRI coils that are tuned to the same radio frequency are positioned close together, which may occur, for example, in phased array coils, the MRI coils may inductively couple to each other, which causes the MRI coils to detune each other. Detuning due to inductive coupling reduces image quality as compared to using single coils individually. Existing phased array coils may address the detuning due to inductive coupling problem by overlapping coils or by using preamplifiers that dampen current flow in individual coils.